Expansible mandrel



June 1, 1937. E. LssER EXPANSIBLE MANDREL 2 Sheets-Sheet 1 Filed NOV.2l, 1955 .772 venfor [ml Lasser Atarngs June l, 1937. E LSSER I2,082,345

EXPANSIBLE MANDREL Filed Nov. 2l, 1935 2 Sheets-Sheet 2 BMgM/Hiorne 5Patented June l, 1937 UNITED STATES PATENT OFFICE EXPANSIBLE MANDRELEmil Lsser, Zurich, Switzerland, assignor to Maag-Zahnrder und-MaschinenA.G., Zu-

rich, Switzerland 9 Claims.

My invention relates to a tool such as a mandrel or gauge which is soconstructed as to be capable of undergoing a deformation changing adimension, for instance a diameter, of the element.

It is common practice to use a mandrel for the attachment of work piecesthereon having an end provided with two or more diametrical slotswhereby separate fingers are formed which may be spread apart bycooperation with a conical core to vary the outer diameter. Such avariation, however, 'involves necessarily a departure of the outersurface of the fingers fro-m their truly cylindrical form. It is anobject of my invention to avoid this disadvantage and to provide amandrel or gauge capable of undergoing a deformation which, whilechanging a dimension of the element, Will not objectionably distort itsgeometrical contour. I attain this object by providing the mandrel orother member with a plurality of Yuniform separate recesses which extendfrom a surface of the member obliquely thereto to a certain depth andare vso spaced with regard to the elasticity of the material that theprojections formed between the recesses are capable of bendingtransversely to the surface. Such bending will vary a dimension of themember measured from the surface as a base. In event of a cylindricalmember, for instance, the slots may extend axially thereto at an angleto kthe diameter of the member toa certain depth and may be socircumferentially distributed and spaced that the arms or projectionsformed between them may be bent, Whereby the diameter of the cylindricalsurface of the member will be varied. Suitable means may be provided forbending the projections or arms the desired extent.

Further objects of my invention will appear from the description ofvarious embodiments following hereinafter and the features of noveltywill be pointed out in the claims.

In the drawings Fig. 1 illustrates a prismatical member of variablewidth,

Fig. 2 a cylindrical mandrel of variable diameter having axiallyextending slots and a work piece fixed thereon, the Work piece beingshown in section,

Fig. 3 the section taken along line 3-3 of Fig. 2,

` Fig. 4 a modified form of a cylindrical mandrel having helical slots,

Fig. 5 an end view of the mandrel shown in Fig. 4 and a work pieceattached thereon, the

normal position of the projecting arms of the mandrel being shown indotted lines, v

Fig. 6 an axial section through an adjustable cylindrical gaugeconstructed in accordance with my invention, the section being takenalong line 6-6 of Fig. 7,

Fig. '7 an end view of Fig. 6,'one of the adjusting nuts being removed,

Fig. 8 a perspective view of the gauge shown in Figs. 6 and 7, theadjusting nuts being removed,

Fig. 9 a cylindrical broaching needle constructed in accordance with myinvention,

Fig. .110 a cross-section of Fig. 9 taken along line Ill-l0 of Fig. 9,

Fig. 11 a section of a modified form of a cylindrical mandrel takenalong line II-II of Fig. 12,

Fig. 12 an end view of the mandrel shown in Fig. 11,'

Fig. 13 an end View of a bushing having a vari u able inner diameterconstructed in accordance with my invention,

Fig. 14 an axial section through a modied form of a bushing .having avariable inner diameter,

Fig. 15 a cross-section through a further modliication of a cylindricalmandrel or gauge, and

Fig. 16 a cross-section through a modication of a lcylindrical hollowtool or machine element having a variable inner diameter.

In Fig. 1 I have shown a prismatical member of substantially squarecross-section which is so constructed in accordance with my invention`that its width a may be varied while its height b and its length c isinvariable. For this purpose, each of the two side faces of the memberis provided with a plurality of uniform separate recesses or slots llllwhich extend from the side face of the member at the acute angle: a ofapproximately forty-.five degrees thereto to a certain depth d which inthe instant case amounts approximately to one quarter of the width ofthe member. The recesses I0 are so spaced that the projections Il formedbetween them are capable of bending transversely to the side face. Sucha bending will res-ult in a variation of the angle a and thus of thewidth a of the member. Viewed from another aspect, the machine elementshown in Fig. 1 may be described as comprising a body portion I2 whichhas a plurality of adjacent projections ll terminating in a commonsurface which is the side face of the member. The length of theprojections Il is so dimensioned withy regard to their thickness and totheir elasticity that the projections may be bent an extent sucient tovaryr the width a of the member the required amount. If desired,suitable means may be provided for bending the projections I I, as willbe described later.

Figs. 2 and 3 illustrate the application of my invention to anexpansible mandrel. 'I'he cylindrical body I2 of the mandrel is providedwith six circumferentially distributed ,longitudinal slots I3 whichextend to such a limited depth-as to form between them projecting farmsI4 which extend over substantially the entire length of the mandrel andhave such a limited thickness indicated at e as to be capable of bendingunder a pressure applied to the arms I4 in radial direction. Preferably,the slots extend tangentially to an imaginary coaxial cylinder' I6 shownin Fig. 3 in dotted lines. The outer face of the arms is preferablyoffset inwardly from the cylindrical contour over the width f asshown atI5. Therefore, the outer end face I 'I of each arm only coincidesnormally with a true cylinder of the diameter g. When a work piece suchas shown at 'i having a slightly smaller interior diameter than g isslipped ony the mandrel, the arms I4 may yield resiliently and the endfaces I'I of the arms I 4-will snugly bear .against the boring of thework piece 'I and the arms I4 will hold the work piece in truly coaxialposition with great power and with great accuracy owing to theconcentrical disposition of the end, faces I1. f

While the slots I3 and the arms I4 formed thereby extend in axialdirection in the embodiment of Fig. 2, they may also extend helically asillustrated in Figs. 4 and 5.. In Fig. 5 the arrangement of the slots isthe same as in Fig. 3

and, therefore, need not be described in detail. However, in Fig. 5 Ihave shown the arms I4 in inwardly bent condition in full lines and innormal condition in dotted lines. The pitch of the helix may be variedin accordancewith the particular requirements provided the windings ofthe helix or helices are so spaced with regard to the elasticity of thematerial of the member that the arms are suicientlycapable of ben-ding.

In Figs; 6, 7 and 8 I have shown an adjustable gauge constructed inaccordance with my invention. The gauge comprises ia spindle 20 formedwith a collar 2l and provided with screwthreads 22 on both sides of thecollar. The edges of the collar are preferably tapered as indicated at23. The collar is provided with six circumferentially distributed.longitudinal slots 24 extending to a certain depth tangentially to theperiphery of the spindle 20, whereby six longitudinally extending arms25 are formed. The outer face of these arms is inwardly offset from theperiphery of the collar, as indicated at k26, except for a marginal zone2-1. Moreover, the end faces of each of the arms are out out, as shownin Fig. 8, so as to reduce the length of the inner portions of the arms,whereas the outer portion of each arm extends between the conical endfaces 23.

These conical end faces are engaged by nuts 28 screwed on the threads22-and provided with suitable inwardly tapered end faces 29. It isevident that when the nuts 28 are tightened, they will force the arms 25inwardly and thereby decrease the distance of the diametrically opposedfaces 2l, that is to say,.the diameter of the gauge. The flexibility ofthe arms is enhanced by the reduction of the length of their innerportions. As any arm 25 will move bodily towards or away from theVcentral axis' of the spindle 2i! without skewing, no matter whether thepressures applied to its end faces are equal or not, the gauge willalways preserve its truly cylindrical form with any adjustment of itsdiameter. While in this particular embodiment the adjustable means 28for bending the .arms 25 are so arranged as to bend them inwardly, it isobvious that these means could be so arranged as to act in the oppositedirection.

In Figs. 9 and 10 I have illustrated a broaching needle constructed inaccordance with my invention. The needle comprises a cylindrical member30 provided with seven circumferentially distributed longitudinal arms3| which are formed by slots 32 extending to a certain depthsubstantially as shown in Figs. 2 and 5. Each arm 3| is provided with acutting edge 8 at its free end, the rake face 33 of the cutting edgebeing formed by grinding a recess into the outer face of the arm 3|. Asthe arms extend at an angle to the diameter of the broaching needle,they will vary this diameter by bending. Owing to the elasticity of thearms 3| provided with the cutting edges 8 the breaching needle is Veryefcient and .accurate in operation.

Figs. ll and 12 illustrate a machine element differing from those shownin Figs. 2, 3, 4 and 5 by the transverse disposition of the slots. Therod or spindle 35 is provided with a plurality of conical collars 36formed by the circumferential slots 31 which extend from the cylindricalouter surface to a certain depth at an acute angle to the axis of theelement. To enhance the exibility each collar 36 is provided with sixradial slots 38, compare Fig. 12, splitting up each collar into sixsector-shaped projections. These projections are so dimensioned withregard to the elasticity of the material as to ensure the requiredflexibility. The element illustrated in Figs. 11 and 12 may be used as amandrel, for instance as that shown in Fig. 1.

In Fig. 13 I have illustrated a bushing 4G having a variable innerdiameter. The bushing is provided with twelve equally spacedlongitudinal borings and with slots 4I extending from the boringsinwardly and opening into the hollow inner space of the bushing. Asthese slots extend at an angle to the diameter of the bushing,

interior resilient arms o r projections 42 are formed. VIf desired,means similar to those illustrated in Fig. 6 may be provided for bendingthe arms 42, whereby the inner diameter of the bushing may be varied.

In Fig. 14 a bushing 43 is shown provided with a plurality of interiorconical collars 44 which are equally spaced by gaps or recesses 46 andprovided with suitable longitudinal slots 45. Each section of a collaris flexible whereby the inner diameter of the collars 44 may be varied.f

In the embodiment illustrated' in Fig. 15, the projections or arms 44are not integral with the member 45 but are produced separatelytherefrom and then suitably united therewith. For this purpose, thecylindrical member 45 is provided with twelve circumferentiallydistributed recesses in which the plates I4 are inserted so as to freelyproject a distance which is sufficiently long with regard to thethickness of the arms 44 to permit them to bend, whereby the distance ofthe outer ends of two opposed arms 44 may be varied. It will be notedthat all of the arms terminate in a cylindrical surface just as do thearms I4 in Fig. 3.

The embodiment of Fig. 16 is similar to that of Fig. 13.1 Thelprojections El, however, are formed by plates which are 4non-integralwith the bushing 50 and are rigidly secured thereto; For this purpose,the interior of the bushing is provided with six circumferentiallydistributed recessesin which the outer ends of the plates 5I areinserted and fixed in place by soldering or welding or the like. It willbe noted that the plates extend at an angle to the diameter of thebushing tangentially to an imaginary cylinder. Their ends may be formedwith shallow recesses 52 conforming to this cylinder, the diameter ofwhich may be varied by bending the plates so as to change their angulardisposition relative to the diameter. Hence, the function is the same asthat of the element shown in Fig. 13.

While I have described my invention in its application to expansiblemandrels or broaching tools, it is to be understood that my invention isapplicable to any tool or machine element, where the variation of adimension is desired.

No specific reference has been made to the material of which the tool ormachine element consists, except for the statement that such materialshould be elastic. The material will be selected to meet therequirements of each particular case. In many instances ordinary steelmay be used.

While I have described various specific embodiments of my invention, Iwish it to be understood that numerous changes may be made withoutdeparting from the spirit of my invention.

What I claim is:

l. A work-holding mandrel adapted to engage a work piece comprising amember of elastic material having a plurality of contact surfaces andseparate uniform recesses intermediate said surfaces and extendingtherefrom and obliquely thereto to a certain depth, and thereby forminga plurality of projections; each of said contact surfaces forming an arcadapted to have blunt stationary contact with said work piece, saidrelcesses being so spaced with regard to the elasticity of said materialthat the projections between said recesses are capable of bendingtransversely to said surfaces whereby the diameter of said mandrel isvariable.

2. A work-holding mandrel adapted to engage a work piece comprising amember of elastic material having a plurality of contact surfaces andaxially extending grooves of uniform width intermediate said surfacesextending therefrom and at an acute angle thereto to a certain uniformdepth, and thereby forming a plurality of projections; each of saidcontact surfaces forming an arc adapted to have blunt stationary contactwith said work piece, said grooves being so spaced with regard to theelasticity of said material that the projections between said groovesare capable of bending transversely to said surfaces whereby thediameter of said mandrel is variable.

3. A work-holding mandrel adapted to engage a work piece comprising amember of elastic material having a plurality of contact surfaces andhelical grooves intermediate said surfaces and extending therefrom andat an acute angle thereto to a certain depth and thereby forming aplurality of projections; each of said contact surfaces forming an arcadapted to have blunt stationary contact with said work piece, saidgrooves being so spaced with regard to the elasticity of said materialthat the projections between said grooves are capable of bendingtransversely to said surfaces whereby the diameter of said mandrel isVariable.

4. A work-holding mandrel adapted to engage a workpiece comprising'altubularf'memb'er of elastic material having a plurality of interiorcontact surfaces and grooves-of uniform width intermediate saidK'surfaces yandoextending therefrom and obliquelythereto to a certainuniform depth, and thereby forming a plurality of projections; each ofsaid contact surfaces forming an arc adapted to have blunt stationarycontact with said work piece, said grooves being so spaced with regardto the elasticity of said material that the projections between saidgrooves are capable of bending transversely to said surfaces whereby theinner diameter of said mandrel is variable.

5. A work-holding mandrel adapted to engage a work piece comprising atubular member and a plurality of separate uniform fingers of elasticmaterial each secured at one end thereof to said member and projectingfrom the inner wall of said member at an acute angle thereto, each ofsaid fingers having an arcuate contact surface at its free end adaptedto have blunt stationary Contact with said work piece and extending adistance, relative to the width of said fingers and their elasticity,suicient to render said fingers capable of bending transversely to saidinner wall whereby the inner diameter of said mandrel is variable.

6. A work-holding mandrel adapted to engage a work piece comprising amember, a plurality of adjacent projections of elastic material securedat one end thereof to said member, each of said projections having anarcuate contact surface at its free end adapted to have blunt stationarycontact with said work piece and extending at an acute angle to saidsurface, the length of said projections being so dimensioned with regardto their width and their elasticity that they are capable of bending ina direction changing said angle whereby the diameter of said mandrel isvariable.

7. A work-holding mandrel adapted to engage a work piece comprising amember of elastic material having a plurality of contact surfaces andseparate uniform recesses intermediate said surfaces and extendingtherefrom and obliquely thereto to a certain depth, and thereby forminga plurality of projections, each of said contact surfaces forming an arcadapted to have blunt stationary contact with said work piece, andadjustable means for bending said projections transversely to saidsurfaces whereby the diameter of said mandrel is variable.

8. A work-holding mandrel adapted to engage a work piece comprising amember of elastic material having conical end faces, a plurality ofcontact surfaces, and circumferentially distributed axially disposedgrooves of uniform width intermediate said surfaces and extendingtherefrom and at an acute angle thereto to a certain depth, and therebyforming a plurality of projections, each of said contact surfacesforming an arc adapted to have blunt stationary contact with said workpiece, and annular members engaging said conical end faces and mountedfor axially y adjustable movement relative to said member, whereby saidprojections are bent in a direction to change said acute angle and thediameter of said member is varied.

,9. A work-holding mandrel adapted to engage a work piece comprising amember of elastic material having conical end faces, a plurality ofcontact surfaces, and circumferentially distributed axially disposedgrooves of uniform width inter- CIL mediate said surfaces and extendingtherefrom and at an acute angle thereto to a certain depth, and therebyforming a plurality of projections, each of said contact surfacesforming an arc adapted to have blunt stationary contact with said workpiece, and annular members engaging said conical -end faces and mountedfor axially adjustable vmovement relative to said member, whereby saidprojections are bent in a direction to change said acute angle and thediameter of said member is varied. v

Y ENEL LASSER.

